Handheld or portable devices, such as personal digital assistants (PDAs), provide a user the flexibility of remotely accessing information sources such as servers, databases and the internet. They are also used to operate software that was originally designed for desktop machines. For example, many Microsoft desktop applications will run on handheld machines. One of the main drawbacks that is encountered when using a handheld device to access these types of information sources is that the image data is not adapted to the smaller display area of the handheld device. In other words, the image does not “fit” within the handheld device's smaller display area.
According to one technique developed to overcome the problems caused by the disparity between the handheld device display area size to the actual image size, only a portion of the image is displayed within the smaller display area. The user can then navigate through the entire image using the hand held devices input interface (e.g., wand, keys, buttons, mouse, etc.) to view the other portions of the image. For instance, if a user remotely accesses a web page with a PDA, only a small portion of the web page is displayed within the PDA display area and the user navigates to other portions of the web page via the user interface. This partial viewing of the image can be confusing and frustrating to the user since it can become unclear where in the image the user is viewing, thereby making navigation through the image difficult. Hence, partial viewing represents one of the major impediments to interacting with information intended for large display devices. One alternative to partial viewing is that the full sized image is “scaled down” into the smaller display area of the small display area device. However, this technique often makes it difficult or impossible to view image details depending on the size of the display area.
In another known technique, instead of equally “scaling down” the whole image, the entire image is displayed in a PDA-type display area by scaling down a selected portion (or region of interest) at a relatively low scaling factor while using a relatively higher scaling factor or factors for the remainder of the image. In this way, the region of interest is readable by the user and the remainder of the image is discernable enough to provide context for navigation. When the user navigates to other portions of the full image with a user interface and selects new regions of interest, the scaling factor of the new region of interest is reduced (i.e., reduced such that the region becomes readable) while the remainder of the image regions including the old region of interest is scaled down using a higher scaling factor. This technique facilitates navigation about a larger image that is displayed on a relatively smaller display area.
In order to display a scaled version of an image as described above, one known method (shown in FIG. 1A) is to convert the image region into a frequency domain representation including a plurality of frequency coefficients and then transmit all the frequency coefficients from the image source to the destination device (e.g. a PDA). Next, the transformation is inverted to obtain a full sized spatial domain image region, and then this image region is scaled down to the desired size in the spatial domain. This method is illustrated in FIG. 1A, such that an image region is converted into a frequency domain representation and a frequency coefficient array 10 is transmitted to the destination device. The inverse transformation converts the array back to spatial image data 11 of the same size as the original image region. Then image region 11 is scaled to the desired size 12. The problem with this method is that it requires the transmission of all frequency coefficients and hence, requires a large amount of bandwidth.
The disadvantage of the method shown in FIG. 1A is that whenever remotely accessing image sources with a handheld device the image data is often wirelessly transmitted over a communication path having a finite bandwidth. A small or overburdened communication path can significantly hinder the users ability to quickly access remote information by limiting the amount of data that can be transmitted between the information source and the handheld device. Hence, there is a strong motivation to reduce bandwidth usage while providing as much information as possible. However, transmitting all frequency coefficients tends to consume a relatively large amount of bandwidth that can potentially result in slow remote access times or an inability to remotely access certain image data. Hence, what is needed is a manner in which to transmit digital images between an image source and a handheld device in a bandwidth efficient manner.
The present invention, in general, is directed towards displaying large images and user interfaces originating from an information source (e.g., a server) within a small display area, such as the display area of a handheld device (e.g., PDA). In addition, this disclosure is directed to providing a system and method of transmitting an image in a bandwidth conservative manner from an information source to a handheld device.